Add more interesting return codes to xdisplaycheck.

In isolate tests we only display the status when failing.

R=maruel@chromium.org, sadrul@chromium.org
BUG=None
TEST=isolated runs, local

Review URL: https://codereview.chromium.org/387143004

Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: aeef559f737ef6305120a2e941dd407d881c3704
diff --git a/xdisplaycheck.cc b/xdisplaycheck.cc
index 1731788..6623153 100644
--- a/xdisplaycheck.cc
+++ b/xdisplaycheck.cc
@@ -84,14 +84,14 @@
                        &event, &err)) {
     fprintf(stderr,
         "Failed to get XInputExtension on %s.\n", XDisplayName(NULL));
-    return -1;
+    return -2;
   }
 
   int major = 2, minor = 0;
   if (XIQueryVersion(scoped_display.display(), &major, &minor) == BadRequest) {
     fprintf(stderr,
         "Server does not have XInput2 on %s.\n", XDisplayName(NULL));
-    return -1;
+    return -3;
   }
 
   // Ask for the list of devices. This can cause some Xvfb to crash.